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How does a Soakaway Work?


A septic tank soakaway ia designed to disperse effluent without a high concentration of solids into sub-soil near the tank.

Soakaway size depends on the following factors,

The porosity of the sub-soil.
The number of residents of the property it is serving.
Whether a septic tank or a sewage treatment plant.

Septic tank soakaways are usually constructed using long trench lines filled with a clean stone containing a perforated distribution pipe. The trenches can be interconnected (a "looped" system), a simple long trench, a "herring bone" layout or a single large pit filled with aggregate.

Soakaway suitability and operation is very much dependant on the permeability of the sub soil. Because of this, it is essential to carry out porosity tests to determine the size and configuration of the soakway needed.

In general, the poorer the sub-soil permeability the more extensive a soakaway system needs to be.

The level of the natural water table in the sub-soil is another important factor in the design and operation of a soakaway. Clearly, soakways can only function effectively if the water-table level is lower than the base of the soakaway.

High water table conditions can be combatted by using an effluent pump unit accommodated either inside the treatment plant or installed separately on the outlet side of a septic tank.
Soak Away - schematic
Soak Away in progress